Both in the clinical sector and in private health care, there is a need for systems and networks which are able to monitor the complex interplay of individual body functions of a patient and, if appropriate, to influence body functions in a targeted manner. By way of example, this can involve care of chronically ill patients, such as diabetes patients, for example. High-risk patients can also be cared for in this way, for example high-risk patients who are known to be at increased risk of infarct. Generally, it should be pointed out that the term “patient” used in the context of the present invention does not necessarily restrict the target group circle to ill human or animal patients, however, rather that, in principle, healthy target groups can also be cared for by means of the devices proposed below. Generally, therefore, the term “patient” can be at least substantially equated with the term “user”.
In many cases, the communication between the individual components of the system presents a challenge in complex medical systems. Medical communication systems are known from various prior art documents. By way of example U.S. Pat. No. 7,161,484 B2 describes a system for monitoring medical parameters of a patient comprising at least one sensor for detecting at least one predetermined medical parameter. Furthermore, a transmission means for transmitting the medical parameters detected by the sensor is provided, wherein the transmission is sent to a remotely arranged server. U.S. Pat. No. 7,163,511 B1 describes a device and a method for frequently measuring the concentration of an analyte in a biological system. In this case, use is made of a monitoring system comprising at least two components in order to facilitate the data collection and the displaying of the data. In US 2007/0027367 A1, a personal area network for receiving, storing, processing, displaying and communicating physiological data is disclosed, which uses an open architecture and which may comprise a personal server, such as a cellular phone. The open architecture allows additional sensors to join the network, without rendering the personal server irrelevant.
Wireless communication in relatively close proximity to patients takes place nowadays predominantly by means of radio systems which utilize the entire electromagnetic field and usually operate in the far field. In the case of far field communication, the distance between a receiver and a transmitter antenna is greater than double the wavelength of the radio carrier frequency chosen. At 2.45 GHz, this is approximately 0.3 m. Diverse radio technologies are standardized under IEEE 802.11 and related standards. In this case, principal features are that an ISM frequency (Industry Science Medical, for example 2.45 GHz) is used and that with a limited transmission power of approximately 100 mW, for example, distances of approximately 1-10 m are bridged. ISM frequencies are generally accessible frequency bands, i.e. frequency bands not allocated by organizations or governments in accordance with strict rules. The only ISM frequency band that can currently be used without restrictions throughout the world whilst observing the presently applicable standards is the 2.45 GHz band.
Furthermore, systems are available that use only the magnetic field component. Only distances within the antenna near field can thereby be bridged, owing to physical conditions. Such systems are in use as RFID systems (Radio Frequency Identification, also called Transponders) or as NFC systems (Near Field Communication). RFID systems are distinguished by the fact that a so-called reader induces data and energy in a so-called transponder. The transponder modifies the data, if appropriate, and returns them to the reader again. The transponder is generally only active if it is situated in the influencing field of the energy of the reader. NFC works using the same structures and protocols as RFID, but in this case the transponder also comprises its own energy source, such that only the communication is activated by the reader, but the application can remain active even outside the influence of the reader. This is advantageous particularly in the case of distributed, continuously measuring sensor systems.
Communication systems which utilize only the electric field component of the electromagnetic field have also been known for some time. Owing to the breakdown strength of air, which is approximately 1000 V/mm, the electric field component can transmit at most only approximately 1/90 000 of the energy of the magnetic field (See e.g. K. Küfmüller et al.: Theoretische Elektrotechnik: Eine Einfürung, 10. Auflage, Springer Verlag, Berlin, S. 333. Therefore, the remote action component is in many cases limited to a direct touching contact.
However, it has been found here that a human body is relatively well suited to conducting dielectric displacement currents. The transmission of items of information is therefore possible without the latter leaving the conducting body over a wide area. Such networks which operate in the near-field range and utilize the human body for transmitting signals are known, in particular, in the field of applications for personal information and communication, for example from U.S. Pat. No. 6,542,717 B1, from T. G. Zimmerman: “Personal Area Networks (PAN): Near-Field Intra-Body Communication”, master's thesis at the Massachusetts Institute of Technology, September 1995, or from M. S. Wegmüller: “Intra-Body Communication for Biomedical Sensor Networks”, dissertation, ETH Zürich, 2007, where such networks are also referred to as PAN (Personal Area Network). Such networks use electric fields as a communication medium between transmitters which are arranged on persons.
Systems which utilize the human body for communicating signals are also known from the medical sector. Thus, U.S. Pat. No. 6,315,719 B1, for example, describes a system which can be used for long-term medical monitoring of a patient, for example an astronaut. In that case, an autonomous sensor unit is arranged on a person's body, said sensor unit having electrodes. These electrodes are arranged on the skin by means of an adhesive strip. Furthermore, a transmitter and receiver worn on the body is provided, which serves as a central unit.
In the field of diabetes diagnostics, in particular, previous developments have generally concentrated on the detection of a small number of individual parameters with direct diagnostic reference. By way of example, glucose from arterial blood or from the interstitium is measured. In this case, a treating physician is generally consulted as a control entity. Said physician also defines the therapeutic measures. Further diagnostic measurement variables or else personal experience and knowledge-based rules are included in this case.
As a result of the development of sensor technology, extended in-vivo diagnostics have become possible nowadays, for example as a result of the possibility of continuously measuring glucose concentrations. As a result of further miniaturization, the detection of various parameters in the blood, for example electrolytes, blood gases, chemical parameters or the like, stress parameters (for example diverse hormones), but also physio-physical parameters (e.g. blood pressure, heart rate, fat content, weight, temperature), becomes possible instantaneously or continuously. Such a system is described in WO 2004/039256 A2, for example.
Over and above these physically and/or chemically measurable variables, diagnosis and therapy are in many cases also influenced by personal factors such as well-being, stress and external influences such as, for example, the weather, time changes or the like, but also events such as eating, periods of sleep, sport or the like. Examples of systems which take account of such factors are described in US 2007/0238934 A1 or in US 2009/0131759 A1. From an overall assessment of the diagnostic values, therapy plans can then be created and implemented.
Suitable actuators make it possible nowadays to a limited extent to implement said therapy plans automatically, in a temporally coordinated manner. Examples of such actuators are an insulin pump, a medicament dispenser, triggering of physiological stimuli or the like.
Diagnostic systems of the type described above therefore consist of numerous complex individual modules with differing handling, start-up, calibration or similar requirements. Precisely in the field of patient self-diagnostics, therefore, it is often the case that simple and hence fault-tolerant start-up and control of the systems and subsystems by the user still do not exist. The construction of diagnostic systems and networks is additionally made more difficult by lack of interoperability or a complicated method of identification and assignment of system components. It is often necessary to manually input long series of numbers, parameters or items of time information, which can lead to a susceptibility of the systems to faults. Moreover, owing to hitherto substantially lacking sensor technology, the inclusion of extracorporeal events, such as eating, sleeping, sport or stress, for example, is generally possible only by manual inputting by the person respectively concerned. This may be associated with the corresponding inputting errors and also errors in the time reference. If a correct temporal assignment is not provided, this can give rise to large diagnostic errors, and the latter in turn to therapy errors.
If a plurality of sensors and/or actuators are intended to be combined to form a common system and are networked, then it is furthermore almost no longer possible for the layperson to coordinate these systems. Operating errors with serious consequences should be expected.
In WO 2007/096810 A1, a body area network (“BAN”) is disclosed, comprising a plurality of devices, each device comprising means for detecting other similar communication devices. A method for setting up the BAN is disclosed, wherein a first sensor device is switched on and searches for other sensor devices by using a request. Since it is the first sensor device, there is no other sensor device responding to the request, and first sensor device is switched to a wait mode. Once a second sensor device is added and switched on, the second sensor device sends a request, which is answered by the first sensor by creating a BAN. The first sensor and a RF device included by this first sensor automatically takes over the role of the coordinator of the BAN.
The setup and method disclosed by WO 2007/096810 A1, however, has some significant shortcomings. Firstly, the role distribution of the setup is fixed in an arbitrary way in that the device, which accidentally is attached to the body first, automatically takes over the role of the coordinator of the network, independent from its physical nature, its hardware and software resources and independent from its requirements in terms of the type of data generated by the device. Since the roles in this network are pre-determined, a situation might easily occur in which the device least suitable for being the coordinator takes over this coordinator role of the network.
Similarly, EP 1 676 525 A1 discloses a medical device communications network comprising a plurality of medical devices having wireless communication circuits. A master wireless communications circuit may be comprised, which may receive medical device information from a plurality of slave wireless communication circuits. The devices exchange device identification codes. The network is set up to thereby monitor that appropriate instruments are matched with appropriate devices.
WO 2008/015627 A1 discloses a system comprising a plurality of network components and a network management device. The components are adapted to communicate by wireless short-range communication. The network management device comprises a body-coupled communication interface and is adapted to configure the plurality of network components by means of the interfaces to form a network and to avoid conflicts between the network components.
Again, as in WO 2007/096810 A1, the networks disclosed by EP 1 676 525 A1 and by WO 2008/015627 A1 have the technical shortcoming that the roles of the network devices are predetermined. Thus, in case there is a master device or management device, the role of this device as a network master is known from the beginning and remains unchanged during operation of the network. The network does not exhibit any flexibility regarding the fact that other devices may be added which might be more suited for taking over the role of the master device. Further, the fixed role-distribution generally is unable to react to changing needs and requirements within the network, such as to a situation in which a network node is added which requires a more time-critical data handling or which requires a modification of the allocation of hardware resources within the network.